[Simh] Lost (18-bit) operating systems

[Bob Supnik]

Before MUMPS-11, there was MUMPS-15. It is the only one of the PDP-15's 
DEC operating systems that is still missing. TA PDF assembly listing of 
XVM/MUMPS-15 (or perhaps only part of it) exists, but it is scribbled 
over in places, as though it were a developer's "in progress" listing.

There's also a pocket card for a PDP-9 timesharing system developed at 
the Ontario Institute for Studies in Education. No other trace has been 
found.

/Bob